D-bond

An example of metal with significant d-bonding is copper. The atomic configuration of copper is... 

Gaseous H CI has a strong absorption band centered at about X = 3.40 X 10 m in the infrared portion of the electromagnetic radiation spec-tmm. On the assumption that D bonds to Cl with the same str ength that H does, predict the frequency of vibration in Hz and rad of D CI. 

Bond Dipole moment D Bond Dipole moment D... 

Hydrolysis of (CH3CHDO)4B in H2O leads to the formation of ethanol retaining the C—D bond formed in the preceding step while forming an O—H bond... 

Solution Properties. Lignin in wood behaves as an insoluble, three-dimensional network. Isolated lignins (milled wood, kraft, or organosolv lignins) exhibit maximum solubiUty in solvents having a Hildebrand s solubiUty parameter, 5, of 20.5 — 22.5(J/cm ) (10 — ll(cal/cm ) > and A// in excess of 0.14 micrometer where A]1 is the infrared shift in the O—D bond when the solvents are mixed with CH OD. Solvents meeting these requirements include dioxane, acetone, methyl ceUosolve, pyridine, and dimethyl sulfoxide. 

Fig. 10. Demagnetization curves of hard magnetic materials A, Nd2Fe B B, Sm(Co, Cu,Fe,Zr)2 C, SmCo D, bonded SmCo E, Alnico 5 F, Mn—Al—C G, Alnico 8 H, Cr—Co—Fe I, ferrite , bonded ferrite. To convert T to G, multiply by 10". ...

B. Cyclohex-2-enones Cleavage of Exocyclic y,d-Bonds and p -Bonding to <3, -Double Bonds... 

If H is replaced by D, p will increase, whereas k will not change, because it is determined by the electronic distribution. Therefore Vd q. The implication of this result can be seen graphically in Fig. 6-19 because of the difference in zero-point energies, the bond dissociation energies of R-H and R-D are different, the energy required to break the R-D bond being the greater. 

Now, since the R-D bond is shorter than the R-H bond, but the electronic natures of H and D are identical, there must be a greater electron density at R in R-D than in R-H. Thus, solely as a consequence of the quantum mechanical zero-point energy... 

Figure 6-20. Bond dissociation curve showing that the average R-H bond distance is greater than the R-D bond distance because of their zero-point energy difference.

A second piece of evidence in support of the E2 mechanism is provided by a phenomenon known as the deuterium isotope effect. For reasons that we won t go into, a carbon-hydrogen bond is weaker by about 5 kj/mol (1.2 kcal/mol) than the corresponding carbon-rfaiiferiwm bond. Thus, a C-H bond is more easily broken than an equivalent C-D bond, and the rate of C-H bond cleavage is faster. For instance, the base-induced elimination of HBv from l-bromo-2-phenylethane proceeds 7.11 times as fast as the corresponding... 

Much evidence has been obtained in support of the El mechanism. For example, El reactions show first-order kinetics, consistent with a rate-limiting spontaneous dissociation process, l- urthermore, El reactions show- no deuterium isotope effect because rupture of the C—H (or C—D) bond occurs after the rate-limiting step rather than during it. Thus, we can t measure a rate difference between a deuterated and nondeuterated substrate. 

Morrison and Migdalof (Ref 14) irradiated o-nitrotoluene and p-nitrotoluene with a Pyrex-filtered mercury lamp using D20 and p-dioxane as solvents. C-D bonds formed with o-nitrotoluene, with no C-D formation for p-nitro-toluene - ... 

The difference in the activation energies is taken to be that between the ground states because the transition states, where no R-H or R-D bond remains, are at the same energy. That is. 

If the R-H and R-D bonds are only partially broken in the transition state, the kie will be smaller than the values shown in Table 9-7. Likewise, if new bonds between H (or D) and a second participating species are beginning to form to an appreciable extent, the kie will also be less. 

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